Buggy code:
public abstract class ClassOrInterfaceView < M extends ClassOrInterface < M > > implements CodeView < M > { protected static final String CLASS_STRING = "class<seq2seq4repair_space>" ; protected static final String INTERFACE_STRING = "interface<seq2seq4repair_space>" ; protected static final String ENUM_STRING = "enum<seq2seq4repair_space>" ; protected static final String IMPLEMENTS_STRING = "implements<seq2seq4repair_space>" ; protected static final String EXTENDS_STRING = "extends<seq2seq4repair_space>" ; protected String onBeforeFields ( CodeGenerator cg , M model ) { } protected Object wrapField ( Field field ) { } protected Object wrapClassOrInterface ( ClassOrInterface < ? > clazz ) { } protected Object wrapMethod ( Method method ) { } protected String onAfterFields ( CodeGenerator cg , M model ) { } private < In , C extends Collection < In > > Collection < Object > wrap ( C models , Function < In , Object > wrapper ) { } protected abstract String classOrInterfaceLabel ( ) { } protected abstract String extendsOrImplementsLabel ( ) { } protected abstract String onSuperType ( CodeGenerator cg , M model ) { } @ Override public Optional < String > render ( CodeGenerator cg , M model ) { <START_BUG> return Optional . of ( ( ( ( ( ( ( ( ( ifelse ( cg . on ( model . getJavadoc ( ) ) , ( s ) -> s + ( nl ( ) ) , EMPTY ) ) + ( cg . onEach ( model . getModifiers ( ) ) . collect ( CodeCombiner . joinIfNotEmpty ( SPACE , EMPTY , SPACE ) ) ) ) + ( classOrInterfaceLabel ( ) ) ) + ( shortName ( model . getName ( ) ) ) ) + ( SPACE ) ) + ( onSuperType ( cg , model ) ) ) + ( cg . onEach ( model . getInterfaces ( ) ) . collect ( CodeCombiner . joinIfNotEmpty ( COMMA_SPACE , extendsOrImplementsLabel ( ) , SPACE ) ) ) ) + ( block ( separate ( onBeforeFields ( cg , model ) , cg . onEach ( wrap ( model . getFields ( ) , ( Field f ) -> wrapField ( f ) ) ) . collect ( Collectors . joining ( ClassOrInterfaceView . scnl ( ) , EMPTY , SC ) ) , onAfterFields ( cg , model ) , cg . onEach ( wrap ( model . getMethods ( ) , ( Method m ) -> wrapMethod ( m ) ) ) . collect ( Collectors . joining ( ClassOrInterfaceView . dnl ( ) ) ) , cg . onEach ( wrap ( model . getClasses ( ) , ( ClassOrInterface < ? > c ) -> wrapClassOrInterface ( c ) ) ) . collect ( Collectors . joining ( ClassOrInterfaceView . dnl ( ) ) ) ) ) ) ) ) ; <END_BUG> } private String separate ( Object ... strings ) { } No newline ; at end ; of file ; }

Fix:
return Optional . of ( ( ( ( ( ( ( ( ( ifelse ( cg . on ( model . getJavadoc ( ) ) , ( s ) -> s + ( nl ( ) ) , EMPTY ) ) + ( cg . onEach ( model . getModifiers ( ) ) . collect ( CodeCombiner . joinIfNotEmpty ( SPACE , EMPTY , SPACE ) ) ) ) + ( classOrInterfaceLabel ( ) ) ) + ( shortName ( model . getName ( ) ) ) ) + ( SPACE ) ) + ( onSuperType ( cg , model ) ) ) + ( cg . onEach ( model . getInterfaces ( ) ) . collect ( CodeCombiner . joinIfNotEmpty ( COMMA_SPACE , extendsOrImplementsLabel ( ) , SPACE ) ) ) ) + ( block ( separate ( onBeforeFields ( cg , model ) , cg . onEach ( wrap ( model . getFields ( ) , ( Field f ) -> wrapField ( f ) ) ) . collect ( CodeCombiner . joinIfNotEmpty ( ClassOrInterfaceView . scnl ( ) , EMPTY , SC ) ) , onAfterFields ( cg , model ) , cg . onEach ( wrap ( model . getMethods ( ) , ( Method m ) -> wrapMethod ( m ) ) ) . collect ( Collectors . joining ( ClassOrInterfaceView . dnl ( ) ) ) , cg . onEach ( wrap ( model . getClasses ( ) , ( ClassOrInterface < ? > c ) -> wrapClassOrInterface ( c ) ) ) . collect ( Collectors . joining ( ClassOrInterfaceView . dnl ( ) ) ) ) ) ) ) ) ;